The present invention relates to improvements in internal combustion engines in general, and more particularly to improvements in so-called split engines. The invention further relates to improvements in friction clutches which can be used in split engines to accelerate one engine unit by transmitting thereto torque from another engine unit.
German Offenlegungsschrift No. 28 28 298 discloses a split internal combustion engine wherein a friction clutch is provided between the coaxial crankshafts of two discrete engine units one of which has a single cylinder and the other of which has two cylinders. The clutch renders it possible to engage the other engine unit with the first engine unit when the power requirements of the contrivance utilizing the split engine, such as a motor vehicle, increase and vice versa. The arrangement is such that each engine unit has its own camshaft and that the friction clutch transmits torque without slippage only when the camshaft of the accelerated other engine unit assumes a predetermined angular position with reference to the camshaft of the one engine unit. A drawback of the split engine which is disclosed in the Offenlegungsschrift is that the clutch cannot ensure full synchronization of the speeds of the engine units when the camshafts assume the aforementioned predetermined angular positions with reference to each other. This means that full engagement of the friction clutch can result in the generation of a pronounced shock which can entail serious damage to the clutch and/or to the parts of the engine units. Moreover, abrupt positive coupling of the two crankshafts to each other adversely affects the comfort of the occupant or occupants of the motor vehicle in which the split engine is put to use. Still further, the friction clutch which is disclosed in the Offenlegungsschrift is not always capable of transmitting full torque, especially if the shock which develops as a result of abrupt full engagement of the clutch entails the transmission of very pronounced torque from the one unit to the other unit or vice versa.